Objective:

We focused this project on two susceptible populations: individuals with neurological disorder, and individuals with diabetes. Using Medicare data to select the susceptible populations, we will estimate county specific mortality risks associated with both short- and long-term exposure to individual pollutants on a national scale. Then we will identify factors that could explain the heterogeneity of these air pollution mortality risks. The specific aims of this proposal are:

Aim 1: To estimate the chronic effects on mortality of long-term exposure to individual pollutants in several US counties in two susceptible populations defined as individuals with neurological disorders or diabetes.

Aim 2: To estimate the acute effects on mortality of short term effects of individual pollutants in a potentially susceptible population.

Aim 3: To investigate whether markers of susceptibility and vulnerability differentially influence the previously established relationships between individual pollutants and mortality, allowing us to identify subpopulations at increased risk for harmful effects of air pollution. Moreover we will examine effect modification due to the composition of multi-pollutant mixtures and to PM composition.

Progress Summary:

In the past years we worked on preparing the data. We finished and we worked and published on the acute effects on mortality and hospital admissions of the short term effects of PM2.5 in individuals with neurological disorder and diabetes. (Aim 2)

We have been working on the chronic effects of PM2.5 in all Medicare enrollees to examine: 1) on mortality across all subjects; 2) on developing a neurological disease.

We started to examine effect modification (Aim 3) by individual and are level characteristics and, when looking at mortality, we also have been looking at particulate composition.

I have also been working in collaboration with Drs Bell and Dominici on two review papers summarizing the scientific evidence regarding effect modification of associations between short-term exposure to ozone and particulate matter and the risk of death or hospitalization.

Preliminary results: this year we submitted 2 abstracts to the ISEE and we also submitted 2 manuscripts (see below). I am adding here the abstracts of the 2 submitted manuscripts which describe our results.

Title: Long-term PM2.5 Exposure and Neurological Hospital Admissions in the Northeastern United States

Background: Long-term exposure to ﬁne particles (PM2.5) has been consistently linked to a series of outcomes. Recently there has been increased interest to examine the effects of air pollution on the nervous system, with evidence showing potentially harmful effects on neurodegeneration. Our objective was to assess the impact of long-term PM2.5 exposure on event time, deﬁned as ﬁrst admission for dementia, Alzheimer’s or Parkinson’s diseases (AD and PD, respectively) in an elderly population across the Northeastern US.

Methods: We examined the effects of PM2.5 on ﬁrst hospital admission for dementia, AD and PD, among all Medicare enrollees >64 years in 50 northeastern US cities (1999–2010). For each outcome, we ﬁrst ran a Cox proportional hazards model in each city, adjusting for prior cardiopulmonary-related hospitalizations and year, and stratiﬁed by follow-up time, age, gen- der and race. We then pooled the city-speciﬁc effects together by employing a random effects meta-regression. We also assessed potential modiﬁcation by green and developed space in each city.

Results: We observed strong effects of long-term PM2.5 exposure on all three outcomes. Specifically, we estimated a HR of 1.46 [95%CI: 1.29–1.66] for dementia, 2.00 [95%CI: 1.70–2.35] for AD and 1.44 [95%CI: 1.22–1.70] for PD per 5 µg/m3 of increase in annual PM2.5 exposures. We observed higher effects in more developed cities and lower effects in cities with more green space for PD and dementia, but not AD.

Conclusions: To our knowledge, this is the ﬁrst study to examine the relationship between long- term air pollution and the most common neurodegenerative diseases and to ﬁnd strong associations for all outcomes. Our ﬁndings provide the basis for more studies, as the implications to public health can be crucial.

Title: PM2.5 and Survival among Elderly in the US: Effect Modiﬁcation by Particulate Composition

Background: Fine particulate (PM2.5) air pollution has been consistently linked to survival, but reported effect estimates are geographically heterogeneous. Exposure to different types of particle mixtures may explain some of this variation.

Methods: We used k-means cluster analyses to identify spatial patterns in PM2.5 composition across the US. We examined the impact of PM2.5 and cluster-speciﬁc PM2.5 on survival among Medicare enrollees in 81 US cities (2000–2010). To approximate randomization of exposure with respect to confounders, we ran by-city Cox models using annual PM2.5 average as the exposure of interest, adjusting for individual data on previous cardiopulmonary-related hospitalizations and stratifying by follow-up time, age, gender and race. This eliminates confounding by factors varying across cities, focusing on year-to-year variations of air pollution around its city-speciﬁc mean and trend. We then pooled the city-speciﬁc effects using a random effects meta-regression. In this second stage, we also included cluster indicators to obtain cluster-speciﬁc PM2.5 effects.

Results: We observed more than 6 million deaths among our study subjects. We found a strong impact of annual PM2.5 concentrations on survival (HR = 1.11, 95%CI: 1.01, 1.23 per 10 µg/m3). This effect was modiﬁed by particulate composition, with higher effects observed in clusters containing high concentrations of nickel, vanadium and sulfate. We observed null or negative associations in clusters with high oceanic and crustal particles.

Conclusions: To our knowledge, this is the ﬁrst study to examine the association between PM2.5 composition and survival. Our ﬁndings indicate that long-term exposures to fuel oil combustion and power plant emissions have the highest impact on survival.

Future Activities:

We will keep on working on the survival analysis in subjects with neurological disease, expanding the analysis to around 200 cities across the US. We will examine again first admission for neurological disease but we will also look at mortality in those Medicare enrollee admitted for neurological disorders, therefore focusing on susceptibility.

We will also examine vulnerability and susceptibility (Aim 3) by county and zipcode level area characteristics, and by individual characteristics.

We will examine ozone, PM2.5 components and pollution mixtures.

We will then focus on other remaining activities outlined in the grant proposal.

Supplemental Keywords:

Progress and Final Reports:

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.